1. Field of the Invention
The present invention relates to a cooling system for a piston of an internal combustion engine and more particularly to a piston cooling system which cools a piston from a back side thereof by jetting oil.
2. Description of the Related Art
As a piston cooling system in a conventional internal combustion engine, there is known a construction in which a cooling oil flow path is formed which communicates with an oil passage which is provided in an internal combustion engine and a nozzle portion is provided on a back side of a piston so that oil is jetted from the nozzle portion.
In this related art, as described in JP-A-2004-124938, for example, there is a construction in which a member which is referred to as an end piece is fitted on a distal end of an outlet pipe (a nozzle portion) which is a pipe member as a member different from the pipe member. In this construction, oil is jetted towards a back side of a piston from a plurality of holes provided in the end piece.
In the construction described in JP-A-2004-124938, however, the end piece is attached externally to the outlet pipe (the nozzle portion) of the pipe member in such a manner that the end piece is fitted on the outlet pipe so as to cover the distal end thereof. Consequently, it is necessary that the end piece is, for example, press fitted in the outlet pipe, or welded or bonded thereto in order to fix the end piece in place. Here, when the end piece is fixed to the outlet pipe through bonding, a bonding facility as well as an adhesive is necessary. In this way, in the fixing method based on welding or bonding, not only is the production facility necessary to be enlarged, but also the production process becomes complicated, leading to a problem that the production costs are increased.
On the other hand, when the end piece is fixed through press fitting, the end piece is pushed into the distal end of the outlet pipe so that the end piece is held therein only with a fastening force exerted in a radial direction of the outlet pipe. However, since an oil pressure to be exerted on the end piece is exerted in an axial direction of the outlet pipe, a press-fit amount at the press-fit portion needs to be large, leading to a problem that the fixing construction is enlarged. Further, in the case of the press-fitting method being adopted, since there is also a possibility that the press-fit portion is loosened by the vibration of the internal combustion engine, the fixing construction needs to be enlarged more to avoid the possible loosening of the press-fit portion in the current situations.